Steam boiler



Aug. 2o, 11140.4

G D. EBBETs Er Al.

STEAM 110111111l NVENTORS bbets george D1 eci g ATTORNEY.

Aug.'20, 1940. G. D. EBBr-:Ts Er Ax. 2,212,115

STEAM BOILER y Filed May 4, 1957 l5 Sheets-sheet 2 o o o o o o 5 I9ooooooooooooocfoooooo ,r11 nrw OOOOO Aug. 20, 1940. G. D. l-:BBi-:Ts ETAl. 2,212,115

STEAM BoILER Filed May 4', 1957 5 Sheets-Sheet 3 George D Ebgg/ENTORSCecil Gay Aug 20, 1940. G. D. EBBETs Er A1. 2,212,115

STEAM BOILER Filed May 4, 1937 5 Sheets-Sheet 4 f INVENTORS7///////////////,'////////////////////////////////////11 1 9M/ye D EbbsHGag/A.

ATrRNEY.

Aug. 2 0, 1940.

G. D. EBBETS ET AL STEAM BOILER Filed May 4. 1937 oooooooo ooooouaFl-c - INVENTOR5 George D. [5b/Jets i Cecil H" @my IEY.

5 Sheets-Sheet 5 Patented Aug. 20, i940 narrar orties STEAM BILER GeorgeD. llbbets, Kenilworth, N. J.; and Cecil H. @Sl-ay, Akron, hio,assignors to The Babcock @c Wilcox: @ernaar Newark, N. J., a corporationof New Jersey application May 4, 1937, Serial No. 140,724

ll) Claims.

This invention relates to the construction and operation of steamgenerating units, and particularly to water tube steam boilers of theBabcock & Y

cated in a zon-e in which the heating gas temper-- atures are sufcientlyhigh to secure the relatively high iinal superheat temperature desired,but yet not sufficient to cause overheating of the superheater tubeswhen the steam ow through the superheater tubes is within the probableoperating range. The liability of such superheater tubes to bevoverheated is considerably increased when the steam flow through the,superb-eater is low, as during starting-up periods before the initiationof an appreciable lsteam flow.

A further problem in steam boilers of the character described is thedifficulty of maintaining a uniform iinal superheat temperature over theboiler operating range. It is known that such convection heatedsuperheaters normally have a iinal superheat temperature curve with arising characteristic with increase in boiler load when the amount ofgases passing over the superheater surface is directly proportional tothe products of combustion.

For the foregoing reasons, it is recognized as highly desirable tocontrol the amount of heating gases passing in heat transer relationwith the convection heated superheating surface. One type of suchcontrol which has been heretofore proposed consists in by-passing avariable portion of the heating gases around the superheater. Suchby-pass arrangements are objectionable as they usually require a specialand expensive construction of the boiler, are not readily adapted forincorporation in existing boilers of standard design, involve the lossof a considerable portion of boiler generating surface having a highrate of heat transfer when the by-pass is closed and inoperative, orrequire the use of control dampers in locationswhere the heating gastemperature conditions are excessive and cause overheating of thedampers or render them ineffective, to the extent that the over-alloperating eiilciency of the unit may be reduced.

(ci. 12a-wisc) a double deck steam boiler of the type described which ischaracterized by its relatively simple and low cost of construction,effectiveness over a wide range or" boiler operating conditions,adaptability for incorporation in existing steam boilers of standarddesign, relatively small amount of low rate heat absorbing surfacerender-ed ineffective when the lay-pass is closed, improved l0- cationand construction of the bypass control dampers, and effective control ofthe amount of heating gases contacting Wtih the superheater tubes over awide range of operating conditions.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by .its use,reference should be had to the accompanying drawings and descriptivematter in which we have 20 illustrated and described preferredembodiments of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a steam boiler constructed inaccordance with the invention;

Fig. 2 is a half section taken on the line 2 2 of Fig. l;

. Fig. 3 is a vertical section showing the damper operating mechanism;

Fig. 4 is a view similar to Fig. 1 of a modied construction;

Fig. 5 is a partial vertical section taken on the line 5 5 of Fig. Ll;

Fig. 6 is ka horizontal section taken on the line E of Fig. 4;

Fig.. '7 is a somewhat diagrammatic sectional elevation of anothermodification;

Fig. 8 is a vertical half section taken on the line 3 8 of Fig. 7; `andFig. 9 is a horizontal section taken on the line 9 5 oi Fig. 7.

The steam boiler illustrated in Figs. 1 to 3 of the drawings is of theBabcock 8l Wilcox double deck cross drum type comprising a lower bank ofhorizontally inclined steam generating tubes lil eX- tcnding betweenvertically arranged sectional downtake anduptake headers il and i2respectively, and arranged acrossI the upper end of a i water cooledfurnace i3 adapted for the burning of fluid fuel, such as pulverizedcoal, oil or gas, in suspension at high rates of heat release.

As shown in Figs. l and 2, the lowermost rows lila of the tube bank arearranged to form a boiler slag screen, while the remaining rows arearranged in vertical alignment. The headers II and I2 are connected bynipples I4 and I5 respectively, to corresponding downtake and uptakeheaders I 6 and I 'I respectively, between which extend staggered rowsof horizontally inclined steam generating tubes I8 forming an uppersteam generating bank. The headers I'I and I6 are connected, byhorizontal circulator tubes I9 and downtake tubes 20 respectively, to asteam and water drum 2l .extending transversely of and above the tubebanks. A space 22 is thus provided between and extending the full lengthof the tube banks.

The steam generating surface described is provided with a baille systemwhich in conjunction with the boiler setting defines a single upflowheating gas pass across the lower tube bank, and a plurality of seriallyconnected upilow and downow gas passes across the upper tube bank. Asshown, a refractory baffle 23 extends from the downtake headers II alongthe uppermost row of tubes I of the lower bank for a portion of theirlength, thence vertically and forwardly through the interdeck space 22and vertically across the tubes I8 of the upper bank. A secondtransverse baille 24 extends downwardly and rearwardly from one side ofa gas outlet 25 to the upper bank and vertically across the same. Thedescribed baille system is well known in steam boilers ofthis type, andin conjunction with the boiler setting provides a single upflow heatinggas pass 30 across the lower tube bank I2 which communicates through atapering portion of the interdeck space 22 with an upflow gas passf3I atthe uptake end of the upper tube bank. The gas pass 3I is seriallyconnected over the upper end of the baillle 23 with a downilow g-as pass32 which in turn communicates below the lower end of the baille 24 witha second upilow gas pass 33 leading to the gas outlet 25. The heatinggases leaving through the gas outlet 25 may be passed through a feedwater economizer, or air heater, o-r both, before reaching the stack.

In steam boilers of the character described the interdeck space 22 isordinarily utilized for a convection heated steam superheater, as thegas temperatures in this section are sufficient to effect the high nalsuperheat temperatures now required in high capacity units, while thesuperheating tubes are protected from excessive heating gas temperaturesin normal operation. by the lower tube bank. As shown, the uptake .endof the interdeck space 22 is occupied by a bank of multiple loopedhorizontally extending superheating tubes 35 arranged in flatside-by-side unitary coils for the full width of the boiler. 'I'helowermost tube leg of each coil is connected to a superheater inletheader 36 at the downtake side of the baille 23, receiving steam fromthe drum 2I through tubes 31. The uppermost tube leg of each coil has aportion extending downwardly along and supporting an inclined portion ofthe baille 23 with its lower end connected to a steam outlet header 38.The uptake end of each superheater tube coil has an expansiblesupporting connection with Aa corresponding nipple I5. With thedescribed boiler construction the heating gases pass upwardly across thelower tube bank, thence upwardly across the superheater tubes 35, andsuccessively through the heating gas passes 3|, 32, and 33 to the gasoutlet.

In accordance with the invention, a heating gas by-pass around thesuperheater is provided by terminating the downtake ends of thesuperheater tube loops forwardly of the baille 23 and embedding the samein the refractory baille 40 extending the full width of the interdeckspace 22 and defining the uptake side of a relatively narrow by-pass 4Ibetween the baille 40 and the baille 23. The baille 40 and the downtakeend of the superheater tubes are supported from an auxiliary header 42extending transversely below the upper bank, and receiving a supply ofwater from certain tubes I Ila in the lowermost row of the upper bank.'I'he header 42 is connected by spaced supporting tubes 43 extendingupwardly intermediate the tubes I8 to the drum 2I. The tubes 43 aresupported by vertical hanger rods 44 carried by the external steel work.A vertical baille 45 extends across the upper tube bank alongside thetubes 43 from the header 42 to the uppermost row of the bank to dene theuptake side of the bly-pass 4I across the tube bank. With the by-pass 4Iopen a substantial portion of the heating gases leaving the lower tubebank would pass upwardly across the upper tube bank without contactingwith the superheating tubes except for the relatively small portionthereof formed by the connections to the inlet and outlet headers. Onreaching the top of the by-pass, the by-passed gases join the heatinggas stream which has passed over the superheater tubes and the combinedgas streams pass over the upper end of the baille 23 and downwardlythrough the gas pass 32.

'I'he heating gas flow through the by-pass is eiectively controlled inthe present construction by means of a row of dampers 50 extendingacross the upper end thereof. Each of the dampers 50 is formed by ashallow rectangular box of heat resistant alloy steel filled with heatinsulating material. Each damper is pivotally supported as indicated atI on the upper end of the baille 45, and when in its closed positionextends along the uppermost row of tubes I8 with its downtake endresting on the upper end of the baille 23. Each damper extends across aplurality of the tubes I8 in the uppermost row of the upper banksubstantially in contact therewith, so that a substantial cooling effectis effected by these tubes on the damper when the damper is in itsclosed position. Even when the damper is in its fully open position,indicated by the broken lines in Fig. 1, the subjacent tubes I8 willexert a substantial cooling effect.

The damper operating mechanism illustrated comprises an adjustable linkrod 52 pivotally connected to the downtake end of the damper and to alever 53 carried by an operating shaft 54 and having an adjustablecounterweight 55. The shaft 54 is a common operating shaft for a numberof dampers and is actuated by a reversible electric motor 56 through aspeed reducer 5'I. A sliding seal 58 is provided in the top of theboiler setting to permit vertical and lateral movements of each link 52.

In the modified steam boiler construction illustrated in Figs. 4 to 6the interdeck superheater 60 extends horizontally in the interdeck spacethe full length of the upilow heating gas pass, with its downtake endsupported from a downwardly and rearwardly inclined extension 6I of theuppermost superheater tube leg of each coil, which in turn is supportedfrom the upper tube bank at Gla. The main boiler baille 62 is formed bytile extending between the tube legs 6I and a row of water tubes 63extending parallel to the tube legs 6I, with their upper ends engaging atransverse header 64 to which spaced groups of tubes in the lowermostrow of the upper bank are connected. The upper portion 62a of the balile62 extending-across the upper tube bank is inclinedto provide taperinggas passes across the upper bank. The lower ends of. the tubes 63 areconnected to a header 59 ,incorporated in the downtake nipples. Hangerrods S1 provide a support for the tubes 63. The transverse baiiiesection 62a divides the space occupied by the upper tube bank into anupflow gas pass 65 and a downflow gas pass 66. The downtake cornerportions of the downlow pass are occupied by the upiiow superheaterby-passes 'lll hereinafter described.

The front wall of each superheater` ,by-pass `'iii is defined by arefractory baiile @il which is supported on and extends upwardly, fromthe tubes 53 at a point adjacent the lower end of the superheater. Theportion of each baiile 68 extending across the upper tubebankisof pouredrefractory, and extends the full height of the upper tube bank. rEheinner side wall of each by-pass, as shown in Fig. 5, is defined by are-brickand plastic refractory wall 69 carried by the tubes S3 andextending throughout the space at the rear of and above the baiiie 52between the baille 68 and the rear wall of the setting. As indicated inFig. 5, the portion of the baille S2 which would be below each by-pass'it is omitted to permit an uplow of heating gases through the1:2y-passes.

The control mechanism for regulating the heating gas flow through eachby-pass consists of three pivoted dampers 'li similar to those shown inFigs. l to 3, movable between the full line closed positions and theVbroken line open positions indicated in Fig. 4. Each of the dampers `isoperated by an adjustable rod 'l2 of heat resistant alloy steelconnected to a common operating shaft i3 by a lifting arm iii. rlheshaft i3 is osoillated by a bell crank lever 'l5 carrying acounterweight 'i6 and connected to a suitable external oscillatingmechanism (not shown) e With the described construction the main path ofheating gas flow from the furnace chamber will be upwardly across thelower tube bank, superheater, and the'portion of the upper tube bank atthe uptake side of the baie 62e. `The gases then turn over the upper,end ofthe baffle 5E@ and pass downwardly through the portion of thedownflow gas pass l@ between the by-passes 'lll to a gas outlet "it, Thearrangement of the bfi-passes and their control dampers in the downtakecorners of the setting vsubstantially reduces the heat transfer to thedampers when in their closed position. When the by-pass dampers arepartly or fully open, a portion of the heating gases-leaving the lowertube bank will by-pass the superheater and iiow vertically past thesidesof the balie t2 into each .by-pass.` rI'he gases iiowing through thelay-passes passover the upper ends of the baies 63 and 59 and join thegas stream ilowing downwardly through the surrounding downlow gas pass 5to the gas outlet 18.

In the modiied construction diagrammatically illustrated in Figs. 7 to9, the superheater tube coils Sil extend the full length of the spacebetween the main boiler b aiie Q33 and theuptake nipples, but as shownin Fig. 8, terminate short of the side walls ofthe setting. A vertical.baffle 82 extends along each side of the superheater between the tubesi8 of the upper bank tothe uppermost tube row of the upper bank to dennea vertically extending superheater b-,y-pass B3 at the uptake side ofthe baffle 23 between one of the baffles s2 and the adjacent side wallof the setting. A row of externally operated control dampers 8i islocated at the `upper end of each bY-pass along the top row of the upperbank. With the described construction the by-passed gaseswill nowupwardly at each side of the gas streamthrough the upow pass at theuptake end, merging with that stream to ow through the subsequent downowand upflow gas passes of the upper bank. ,f

. In all of the boiler constructions illustrated the superheater by-passor .by-passes are formed by vertical non-tortucus upflow gas passages.The pressure drop through these passages. is conse, quently utilized forheat transfer purposes rather than in effecting changes in .direction ofthe gas ow. The pressure drop through each by-pass will obviously belower than through the gas pass containing the superheater,andconsequently an effective control of the hea-ting gas ow across thesuperheater canv be maintained even at low boiler ratings. The only heatabsorbing surface included in each yby-pass is part of the upper 'bankof generating tubes which operate with a substantially lower rate oi?heat absorption than the surface in the lower bank, thus utilizingsecondary heating surface of the boiler to secure adequate protection ofthe by-pass control dampers and reduce .the gas temperature sufficientto maintain overall unit thermal efficiency. The construction andlocation of `these dempers and their operating .mechanism not onlyinsures a long life in operation but also the absence Iof any warping ofthe dampers lpermits the control mechanism to be maintained fullyeective. The tube and baffle support o the dampers in their closedposition reduces the stresses on the damper operating mechanism. Aneiiective control of the heating gas ow across the superheater is thusprovided which can be employed to by-pass a major portion of the heatinggases around the superheater during starting-up periods to avoidoverheating -of the superheater tubes, and during normal `operation tocontrol the nal superheat temperature 'as desired. i

While in accordance with. the provisions of the statutes we haveillustrated and described herein the preferred forms of thev inventionnow known to us, those skilled in the art will understand that changesmay .be made in the form of theI apparatusdisclosed without departingfrom the spirit of the invention covered by the claims, and that certainfeatures of the invention may sometimes be used to'advantage without acorrespon-ding use of other features. i

We claim: i.

1. Av steam boiler having upper and lower vertically; spacedfbanks ofhorizontally inclined steam generating tubes, a steam superheater havinga plurality of steam superheating tubes occupying a portion oi the spacebetween said tube banks adjacentcneend thereof, bafiie means arranged todenne a plurality of serially connected up-lowV and downow gas passesacross said upper bank with .said superheater arranged directly belowthe first upflow gas pass, sbaflie means arranged to define `an upiiowheating gas by-pass about said su-perheater tubes extendingsubstantially vertically'across said space and `said upper bank and atone side of said superheater, and damperineans at the upper end of saidby-pass for controlling the gas flow through saidgby-p-ass.

2. A steam boiler having upper and lower vertically spaced banks ofhorizontally inclined steam generatingtu'bes,- a steam superheaterhaving a pluralityof steam superheating tubes occupying a portion4 ofthe space between vsaid tube banks adjacent one end thereof, baillemeans arranged to dene a plurality of serially connected upflow anddownow gas passes across said upper bank with said superheater arrangeddirectly below the rst upilow gas` pass, baille means arranged to definean upilow heating gas by-pass about said superheater tubes extendingsubstantially vertically across said up-per bank and at one side of saidsuperheater, and damper means for controlling the gas flow through saidlby-pass extending along lthe uppermost tube row of said upper bank.

3. A steam boiler having upper and lower vertically spaced banks ofhorizontally inclined steam generating tubes ha-ving uptake and downtakeconnections to the upper and lower ends thereof respectively, .a steamsuperheater having a plurality of steam superheating tubes occupying aportion lof the space between said tube banks adjacent the uptake endthereof, baille means arranged to .denne an upilowheating gas by-passabout said superheater tubes extending substantially vertically acrosssaid upper bank and at one side of said superheater, and ldamper meansfor controlling the gas flow through said by-pass extending Ialong theuppermost tube row of said upper bank.

. 4. A steam :boiler having upper and lower vertically spaced banks ofhorizontally inclined steam generating tubes, a steam superheater havinga pluralityV of steam superheating tubes. occupying a portion of thespace between said tube banks adljacent one end thereof, baille meansarranged to dene a single upflow heating gas pass across said lower bankand a plurality of serially connected upilow and downlow gas passesacross said upper bank with the iirst upilow pass across Said upper bankopening to the upflow pass across said lower bank and said superheaterarranged in said upilow gas stream, baille means arranged to deiine anupflow heating gas `:by-pass about said superheater tubes extendingsubstantially vertically across said upper bank at oneside oi saidsuperheater, and pivotally mounted damper means for controlling the gasflow through said by-pass extending along the uppermost tube row of saidupper bank.

5. A steam boiler having upper and lower vertically spaced banks ofhorizontally inclined steam generating tubes having uptake and downtakeconnections to the upper and lower ends thereof respectively, a steamsuperheater having a plurality of steam superheating tubes occupying .aportion of the space between said tube banks adjacent one end thereof,baille means arranged to define an upflow heating gas pass across saidlower bank and a serially connected upilow gas pass across .the uptakeend of said upper bank with said superheater arranged between saidbaffle means and the uptake end of the boiler, baille means arranged todefme an upflow heating gas by-pass between said superheater and saidilrst mentioned baille means and extending across said upper bank, anddamper means at the upper end ofA said by-pass for controlling the gasVrality of steam superheating tubes occupying a portion of the spacebetween said tube banks adjacent the uptake end thereof, baille meansarranged to define an upflow heating gas pass across said lower bank anda serially connected upflow gas pass across the uptake end of said upperbank with said superheater arranged between said baille means and theuptake end of the boiler, baille means arranged to deiine a substantialvertical heating gas by-pass .between said superheater and said rstmentioned baille means and extending across said upper bank, and dampermeans for controlling the gas flow through said by-pass extending alongthe uppermost tube row of said upper bank.

7. A steam boiler having upper and lower vertically spaced banks ofhorizontally inclined steam generating tubes having uptake and downtakeconnections rto the upper and lower ends thereof respectively, a steamsuperheater having a plurality of steam superheating tubes occupying aportion of the space between said tube banks adjacent the uptake endthereof, baille means arranged along one side of said superheater anddefining a plurality of serially connected upflow and downflow gaspasses across said upper bank, baille means arranged to deiine an upflowheating gas by-pass about said superheater tubes extending substantiallyvertically across said upper bank at the downilow side of said rstmentioned baille means, and damper means at the upper end of saidby-pass for controlling the gas flow through saidby-pass.

8. A steam boiler having a setting rectangular in horizontalcross-section and including upper and lower'vertically spaced banks ofhorizontally inclined steam generating tubes having uptake and downtakeconnections to the upper and lower ends thereof respectively, a steamsuperheater having a plurality of steam superheating tubes occupying aportion of the space between said tube banks add acent the uptake endthereof, baille means arranged along fthe downtake side of saidsuperheater 'and deming a single upilow heating gas pass across saidlower bank and a plurality of serially connected upilow and downflow gaspas-ses across said upper bank, baffle means arranged to define anupflow heating gas by-pass about 'said superheater tubes extendingsubstantially vertically across one corner portion of said setting andsaid upper bank at the downtake side of said ilrst mentioned baillemeans, and damper means for controlling the gas ilow through saidby-pass.

9. A steam boiler having upper and lower vertically spaced banks ofhorizontally inclinedy steam generating tubes having uptake and downtakeconnections to the upper and lower ends thereof respectively, a steamsuperheater having a plurality of steam superheating tubes occupying aportion of the space between said tube banks adjacent the uptake endthereof and spaced from the remaining opposite sides of said boiler,baille means arranged to dene upfloW heating gas bypasses extendingsubstantially vertically across said upper bank at said opposite sidesof said superheater, and damper means for controlling the gas ilowthrough said :by-passes.

10. A steam boiler having upper and lower vertically spaced ibanks of`horizontally inclined steam generating tubes having uptake and downtakeconnections to the upper and lower ends thereof respectively, a steamsuperheater having a plurality of steam superheating -tubes occupying aportion of the space between said tube banks adjacent the uptake endthereof and spaced from the remaining opposite sides of said boiler,baille means arranged along the downtake side of said superheater anddefining a single upflow heating gas pass across said lower bank andseparating upiioW and doWnfloW gas passes across said upper bank, otherbaHe means arranged to dene upow heating gas Iby-passes about said4superheater tubes extending substantially vertically across said upperbank at the upflow side of said rst mentioned baffle means and at saidopposite sides of said superheater, 'and' damper means for controllingthe gas flow through said by-passes.

